Voltage-regulator for series-wound electric generators.



PATENTED APR. 23, 1907.

J. W. WELSH.

VOLTAGE REGULA OR FOR SERIES WOUND ELECTRIC GENERATORS.

APPLICATION FILED 0GT.1. 1906.

2 SHEETS-SHEI1T l.

l I? r '1 Mg IIIIIIIIIIIIIIIII'E' H 3 9 wt 8 nui- FIIlE- No. 851,461. PATENTED APR. 23, 1907 J. w. WELSH. VOLTAGE REGULATOR EOE SERIES WOUND ELECTRIC GENERATORS.

APPLICATION FILED 0CT.1. 1906.

2 SHEETB-SHEET 2.

FIRE- f m m JAMES WINFIELD WELSH, OF EDGEWOOD PARK, PENNSYLVANIA.

VOLTAGE-REGULATOR FOR SERIES-"WOUND- ELECTRIC GENERATORS.

' speciflcation of Letters Patent.

Patented April 23, 1907,

Application filed October 1,1906. Seria Il 336,902.

To all whom it may concern.-

Be it known that I, JAMES WINFIELD WELSH, residing at Ed ewood Park, in the wise exceed, in consequence of the speed at I .as are ordinarily used in street railways.

which the armature revolves or in conseguence of a change in the amount of current rawn from the armature.

My invention has practical application in the operation of electrically driven cars, suclh t is common practice to employ the motor-or -motors with which such car is e uipped as a generator or generators for the rake mechanism. In other words, such a car is equipped with motors which, while the car is running, receive through the trolley or other conducting feeder the current from a distant source, and (driven by that current) cause the car to travel. When, however, the. current so received is cut off, as it is when the car is to be stopped, it is common practice to use the motors, (which continue to revolve as long as the car travels), as a source of an electric currentthat is, as generators themselvesand to use the electric current so generated to stop the car. The generation of an electric current and the utilization or dissipation of the ener thus made available effects the braking. hile the energy may be dissipated, in the form of heat or otherwise, or may be utilized in an desired manner, it is common practice to rive a frictional brake mechanism by the current thus generated.

For electric traction purposes experience has shown that series-wound motors are most suitable; but when the motor becomes itself a generator, and the current generated is em loyed to effect the braking, it has been foun that shunt-wound machines are better. One of the difficulties which has heretofore existed in the use ofseries-wound motors as generators in braking the car is the fact that the electro-motive force of the current generated by the motor (when acting as a generator) may become so great that in practical service it may injure or destroy the motor itself.

My invention is directed to a means for preventing such a deleterious or injurious rise in electro-motive force.

Such a means is diagrammatically illustrated in Figure 2 of the accompanying drawings. Fig. 1 shows in detail and in longitudinal section the device for making and reaking contact wherein the essence of my invention resides. Figs. 3 and 4 are diagrammatic views showing alternative arrangements of details.

In these drawings the armatures of the motors which are acting as enerators are indicated at 1; the fields of t e motors are coils, 2;

3 indicates the brake device, which may be of any character, or as suggested above it may be merely a resistance for dissipating electric energy;

4 is a controller resistance, such as is ordinarily employed in these constructions.

An electric contact, 5, as will be observed, offers, when closed, a path for the flow of the electric current around or in shunt with the field, 2, of the motors now acting as enerators. In this path may he placed, if esired, a resistance, 12. Referring particularly to Figs. 1 and 2, the closing and opening of this contact 5 are effected in the following manner. The movable member of the contact moves in response tomovement of'and is preferably carried by the armature of an electro-magnet, 6; and the energizing of the electro-magnet effects the advance of the armature and the closing of the contact. The electro-magnet receives the energizing current from the generators. The terminals of the coil of magnet 6 are so connected with the armatures of the generators, that the strength of the current which energizes the electro-magnet is rendered dependent directly upon the electro-motive force of the current generated, or in other words, upon the difference in potential across the armatures of the generators. Consequently, the pull which the electro-magnet exerts upon its armature is directly dependent upon and proportionate to the electro-motive force generated in the armatures of the generators. To this end the coil of electro-magnet (j is connected, and preferably as shown .in the find a spring a convenient means.

drawings immediately connected, across the tension of spring 7 determines primarily the generator brushes. The pull of electro-magnet 6 is opposed by a force tending to hold the armature away from the magnet, and accordingly tending to keep the contact device open. Any preferred means affording such an opposing force may be employed; and I Furthermore, since the attractive force or pull of an elcctro-magnet upon its armature increases in. intensity as the armature approaches contact, I find it desirable to employ means which shall exert an increasing opposing force as the armature approaches its magnet.

To this end I find it convenient to employ a' plurality of springs which shall come successively intoplay as the armature advances in response to the magnets pull. In Fig. 2 of the drawings I have shown two springs,7 and 8, the one exerting tension upon. the armature throughout its range of movement, and the other coming into play as the armature approaches the magnet, and thusaugmenting the opposing force. In Fig. 3 are shown three springs, comin thus into play successively. be increased indefinitely.

The parts being arranged as described, the

' contact 5 bein open, motors 1 acting as generators, it will be seen that the current is flowing to operate the brake mechanism, and

the arts Will continue in this position so long as t e electro-motive force does not exceed the predetermined criticalpoint. This predetermined critical point is dependent rimarily upon the tension of spring 7; an as soon as the electro-motive force rises above that point, the pull of the electro-magnet 6 will be so great as to operate its armature, overcoming the tension of spring 7, and closing or tending to close contact 5. As soon as this contact 5 is closed, there is a short circuit or a path of low resistance established around the fields of the generators and a greater or less amount of the current flowing through this path of low resistance will at once effect a diminution in the-electro-motive force of the current produced by the generators. It will be observed, further, that, in the use of a plurality of springs, not

only is there compensation for the increase in intensity of the pull of the ma net upon its armature as the latter approac es; there is also a possibility of more exact control of the voltage. Thus, havin but a single spring, as 7, the contact will close when the voltage rises to a certain point. But, since the pull of the magnet is greater when the armature is in contact with it, the volta e must fall to a greater or less extent below t e critical point, before the tension of spring 7 can effect the retraction of the armature and the reopening of contact 5. With an additional spring 8, however, a finer adjustment is possible, and the range of voltage reduced. The

Manifestly, t e number may voltage ofclosure; the combined tensions of all the springs employed determines the voltage of opening. Screws 9 may be employed for adjusting the tensions of the several springs. It will thus be seen that this contact device is a safety device coming into play at a critical point in the rise of electromotive force to prevent a further rise and guard against injury to the apparatus itself, and the voltage of the current will b ythis automatic device be maintained at a certain predetermined value, or within certain prearranged limits.

As illustrated in Figs. 3 and 4, electro-magnet 6, instead of operating the contact-closing device directly, may operate it through an intermediate instrumentality. In Fig. 3' such an intermediate instrumentality is shown as a relay circuit, 10; and in Fig. 4 a pnermatic motor, 11, is employed whose controlling valve is shifted by electro-magnet 6.

I claim as my invention:

1. In combination with aseries-wound electric generator, a voltage regulator which consists of a shunt circuit around the field of said generator, a make-and-break device in said shunt circuit, an electr c-magnet con-" nected across the generator brushes and controlling said make-ancl-break device, substantially as described.

2. In combination with a series-wound electric enerator, a path for the flow ot' current in s unt around the field of said generator, a make-and-break device in said shunt path, an electro-magnet whose coil is connected across the generator brushes and whose armature in movement operates said make-and break device, substantially as described.

3. A voltage regulator for a series-wound electric generator, which consists of a contact-maker, closing to offer a path for the flow of electric current around or in shunt with the field of the generator, an electromagnet having its coil connected across the generator brushes and its armature attracted to close-said contact-maker against a predetermined opposing force, substantially as described. g

4. A voltage regulator for a series-wound electric generator consisting of a conductor,

offering a path for the flow of electric current around or in shunt with the field of the generator, in which is a circuit opening and closing device, an electro-magnet whose terminals are connected across the generator brushes and whose armature is attracted to .close the circuit opening and closing device,

and means for offering an increasing opposing force to the armature of the magnet as it moves in responseto the pull of said magnet,

substantially as described.

5. A voltage regulator for a series-wound electric generator which consists of a (IICUJiJ opening and closing device to open and close a path for'the flow of electric current around or in shunt with the field of the generator, an electro-magnet whose armature in its movement operates the said opening and closing device, the terminals of said eleotro-magnet connected across the generator brushes,

means for holding the armature of said electro magnet against response to its attractive force until such attractive force shall exceed a predetermined amount, and further means which come into operation as the said armature of the electro magnet responds to the attractive force of the magnet for resisting the pull which the electro-magnet exerts on its armature, substantially as described.

6. A voltage regulator for a series-wound electric generator which includes an electromagnet whose terminals are connected across the generator brushes, a movable contact which in its movement makes and breaks a path for the flow of electric current around or in shunt with the field of the generator and whose movement is effected by the movement of the armature of the said electro magnet, a plurality of restraining means coming successively into play as the armature approaches the electro-magnet and tending to hold the armature the attractive force of the electro-magnet, substantially as described.

7. In combination with a series-Wound direct-current motor adapted to act as a generator, an excess-voltage regulator which consists of a contact-maker', closing to oiler a path of low resistance in shunt with the field of the generator, and means forclosing the contact-maker, said means including an electro-magnet connected across the generator brushes, and means for holding the contactmaker against closure until the pull of the electro-magnet exceeds a certain predetermined strength, substantially as described.

In testimony whereof, I have hereunto set my hand.

JAMES WINFIELD WELSH.

Witnesses:

WILLIAM H. WILsoN, CHARLES BARNETT.

against response to- 

